Isolating the Larsen-C Ice Shelf Mass Instability

1988年，为了回应公众对全球变暖和地球臭氧层空洞等问题日益增长的担忧，世界气象组织（World Meteorological Organisation）和联合国（United Nations）成立了一个由专家科学家组成的国际小组，收集有关气候变化的信息。从那以后，该小组的主要发现表明，气温和海平面上升的速度比自然变化所能解释的要快，而20世纪工业化产生的污染物是一个可能的因素。当今地球的气候变化与极地地区的冰冻结密切相关。随着气温上升，冰融化并流入海洋，导致海平面上升。这种简单关系的代价可能是巨大的。如果南极洲的冰迅速融化，将使全球海平面上升65米，这一变化将淹没包括伦敦在内的世界20个最大城市中的13个。地球上一些最快的气候变化发生在南极半岛，这是南极洲最温暖的地区，位于智利和阿根廷的正南。自19世纪早期的探索以来，那里的气温测量显示，在过去的100年里，气温上升了5摄氏度以上。也许最剧烈的气候变化发生在过去的十年里，1995年和2002年，漂浮的拉森冰架的巨大部分——拉森a和拉森B，每个大约康沃尔的大小——解体成成千上万的冰山，引起了广泛的恐慌。这些事件，在去年的大片《后天》中被描绘成一个孤独的裂缝破裂，是真正的灾难，可能是唯一一个在好莱坞电影中被轻描淡写的自然灾害。更重要的是，这些崩塌让科学家们不确定是什么导致了它们，以及它们将如何影响我们未来的气候。每次崩塌之后，漂浮的拉森冰架曾经存在的地方都会出现新的河口，这些海湾内陆的冰川加速融化，每年融化的冰足以使全球海平面上升0.1毫米。虽然这个数量看起来很小，但科学家们现在担心的是在剩余的拉森- c部分上游更大的冰原，那里包含的冰足以使全球海平面上升50多毫米。如果拉森- c部分坍塌，这些冰将面临严重风险。我们设计了一系列实验，结合卫星和实地考察，来解开拉森冰架崩塌的谜团。我们的测量将确定是海洋的变化还是大气的变化造成的。我们将使用一种灵敏的雷达系统（类似于道路测速摄像机）来测量冰架厚度每小时约0.1毫米的极慢变化。我们还将钻穿冰架的顶层，提取冰芯，这就像树木的年轮一样，告诉我们过去一个世纪里气候是如何变化的。当与新的冰流和冰薄的卫星测量相结合时，我们的实地测量将使我们能够探测到漂浮的拉森冰架下的海洋是否比预期的要温暖，或者夏季表面的冰融化是否比预期的要大。一旦确定了崩塌的原因，我们将建立一个冰架的计算机模型，以调查未来它可能如何断裂。我们的实验将找出1995年和2002年拉尔森冰架灾难性崩塌的原因。他们还将决定剩余的拉森- c部分在未来几年是否会变得脆弱。而且，最重要的是，我们将预测如果拉森- c在未来某个时候崩溃，全球海平面将以多快的速度上升。

In 1988, the World Meteorological Organisation and the United Nations set up an international panel of expert scientists to collect information about climate change, in response to growing public concerns about issues such as global warming and the hole in Earth's ozone layer. Since then, the panel's major findings have shown that air temperatures and sea levels are rising faster than can be explained through natural changes, and that pollutants from 20th Century industrialisation are a likely factor. Earths' present-day climate changes are closely related to the ice frozen in its polar regions. As air temperatures rise, ice melts and drains into the oceans, causing sea level rise. The costs of this simple relationship could be enormous. There is enough ice frozen in Antarctica to raise global sea levels by 65 m if it were to rapidly melt, a change that would flood 13 of the worlds 20 largest cities including London. Some of the fastest climate changes on Earth have taken place at the Antarctic Peninsula, the warmest sector of Antarctica, due south of Chile and Argentina. Air temperatures measured there since early explorations in the 19th Century, show a warming of more than 5 degrees C during the past 100 years. Perhaps the most dramatic climate changes ever witnessed have occurred during the last decade, when, in 1995 and 2002, giant sections of the floating Larsen Ice Shelf - Larsen-A and /B, each about the size of Cornwall - disintegrated into thousands of icebergs, causing widespread alarm. These events, depicted as a solitary crevasse fracture in the opening scene of last years blockbuster The Day After Tomorrow, were truly catastrophic, and are probably the only natural disaster ever to be understated in a Hollywood movie. More importantly, the collapses have left scientists unsure as to what caused them and how they might affect our future climate. In the wake of each collapse, new embayments have been revealed where the floating Larsen Ice Shelf used to exist, and glaciers inland of these bays have accelerated, calving enough extra ice to raise global sea levels by 0.1 mm each year. Although this amount seems small, scientists are now concerned about the much larger ice field upstream of the remaining Larsen-C section, which contains enough ice to raise global sea levels by over 50 mm. That ice would be seriously at risk if the Larsen-C section were to collapse. We have designed a series of experiments, combining satellites and field exploration, to solve the mystery of Larsen Ice Shelf collapses. Our measurements will identify whether changes in the ocean or the atmosphere were to blame. We will use a sensitive radar system / similar to road speed cameras - to measure extremely slow changes in the ice shelf thickness of about 0.1 mm per hour. We will also drill through the top layers of the ice shelf and extract cores of ice, which, like tree rings, tell us how climate has changed over the past century. When combined with new satellite measurements of ice flow and thinning, our field measurements will allow us to detect whether the ocean beneath the floating Larsen Ice Shelf is warmer than expected, or whether summertime ice melting at the surface is greater than expected. Once the cause of the collapses has been identified, we will build a computer model of the ice shelf to investigate how it might fracture in the future. Our experiments will identify the cause of the catastrophic Larsen Ice Shelf collapses in 1995 and 2002. They will also determine whether the remaining Larsen-C section will become vulnerable in the coming years. And, most important of all, we will predict how fast global sea levels will rise if the Larsen-C collapses at some time in the future.